As a method of forming a thin film that is used to manufacture a semiconductor device such as a flash memory or a dynamic random access memory (DRAM), a chemical vapor deposition (CVD) method has been known. The CVD method is a method in which a gas-phase reaction of a source gas and a reactive gas or a reaction at a surface of a substrate is used and a thin film having an element included in a molecule of the source gas as a component is deposited on the substrate.
Also, as a method of forming a thin film, there is a method of forming a thin film on the substrate by sequentially passing the substrate through a processing region in which the source gas is supplied and a processing region in which the reactive gas is supplied, instead of changing a gas atmosphere in a process chamber.
However, only passing through the processing region in which the source gas is supplied and the processing region in which the reactive gas is supplied, the reaction caused by the reactive gas is insufficient. Therefore, residues such as some components of the source gas may remain in the thin film formed on the substrate.